Topsheets used in absorbent articles, such as disposable diapers and sanitary napkins, are required to have not only absorption characteristics such that liquid body waste, e.g., urine or menstrual blood, is smoothly transferred to an underlying absorbent member but surface characteristics for not causing discomfort and skin troubles, such as an itch and a rash, due to overhydration.
Various kinds of topsheets of the type having an uneven surface on the wearer's side have hitherto been proposed. Most of the shapes of the unevenness of this type of topsheets are designed aiming at improvement on the above-mentioned absorption characteristics or improvement on feels such as softness to the touch, and conventional topsheets still have room for improvement to eliminate discomfort or skin troubles due to overhydration.
JP-A-9-111631 discloses wrinkled nonwoven fabric with a great number of streaky wrinkles arrayed on its surface, which is used as a topsheet of an absorbent article. However, the wrinkled nonwoven fabric is deformed easily in the thickness direction under pressure applied while worn, and the gaps between wrinkles are easily collapsed to lose breathability, which can cause discomfort or skin troubles due to overhydration.
JP-A-2000-135239 discloses an absorbent article, such as a sanitary napkin, in which a liquid-permeable nonwoven fabric sheet forming a large number of ridges is used as a topsheet to be brought into contact with the wearer's skin. Japanese Patent 3181195 discloses nonwoven fabric useful as a female component of a mechanical fastener system used, e.g., in disposable diapers, which fabric is composed of a first fiber layer and a second fiber layer partially joined together by thermal fusion, either one of the first and second fiber layers being thermally shrunken to raise the other to form regular projections.
The ridges described in JP-A-2000-135239 are easy to crush by the pressure while in use, impairing the permeability during wearing an absorbent article.
Having a large number of very fine bosses and depressions which are apt to make a hard material, the nonwoven fabric described in Japanese Patent 3181195 impairs the feel of touch during wearing and is not designed for suppressing discomfort or skin troubles due to overhydration. Therefore, the nonwoven fabric of Japanese Patent 3181195 is difficult to use as a topsheet of an absorbent article.